Every puzzle in this app is a 27-clue grid with exactly one solution — verified in advance, so there's always a logical path through, never a guess required. "Extreme" is the hardest tier in this app by a real measure, not just by name: every single puzzle requires a full alternating inference chain (X-Cycle, XY-Chain, or AIC) before it gives way — nothing here stops at Wings or colouring. On average that's about 17 non-Singles moves per puzzle, which is actually higher than "Diabolical"'s average of 12. If you've cleared every other difficulty, this is the real test.
Import a puzzle
Paste 81 numbers, in almost any format: comma- or space-separated, a 9×9 grid, or one long string. Use 0 or . for empty cells — box-drawing separators (| and ---+---) are fine too.
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